StarDate Podcast

The Pilbara region of Western Australia is big, dry, and wide open. And it may contain the oldest cosmic “scar” on Earth: an impact crater gouged three and a half billion years ago. Scientists discovered evidence of the crater during a brief expedition in 2021. They found some rock formations called shatter cones. Some of the cones are as tall as a house. The only known way to make them is in giant collisions with space rocks. Follow-up work last year revealed many more of these formations. The cones were found in a rock layer that’s miles wide, but only a few dozen feet thick. The layer also contains tiny “beads” that formed when molten rock was blasted high into the sky. The flight through the air sculpted droplets of the molten rock into balls. Geologists found that the layer formed three and a half billion years ago, so that’s when the impact must have taken place – more than a billion years earlier than the previous record holder. The asteroid could have been miles wide, and blasted a crater more than 60 miles across. The effects of the collision would have been felt around the world. In fact, researchers say the impact could have helped shape the world. Major asteroid impacts could have traveled deep, churning things up far below the surface. That could have created the “seeds” that gave birth to the continents when Earth was young. We’ll talk about potential future impacts tomorrow. Script by Damond Benningfield

You can’t tell just by looking, but the universe undergoes constant change. Stars explode. Quasars flare up. Asteroids zip past Earth. And soon, astronomers will be able to generate super-high-definition movies of those changes almost every night of the year. That’s because a new telescope dedicated to “time-domain” astronomy is about ready to take its first looks at the heavens. The telescope is the centerpiece of the Vera Rubin Observatory. It’s named for an astronomer who provided strong evidence for the existence of dark matter. It’s atop an 8700-foot mountain in Chile. The telescope’s main mirror, which gathers and focuses starlight, is 8.4 meters across – almost 28 feet. It has a wide field of view, allowing it to photograph the entire southern sky every few nights. It’ll record its observations on the largest digital camera ever built – 3200 megapixels. Astronomers will use those observations to learn more about dark energy and dark matter, and to map the Milky Way Galaxy. And they’ll watch for things that change. They’ll discover asteroids and comets – both close to Earth and deep in the outer solar system. They’ll see novas, supernovas, and other brilliant flare-ups. And the observatory will send out immediate notices of each new outburst, allowing other astronomers to make detailed follow-up observations – learning much more about our constantly changing universe. Script by Damond Benningfield

Before astronauts could land and walk on the Moon, NASA had to be sure they could do three things: live in space for days at a time, catch and link up with other spacecraft, and work outside their ship. And it took stabs at two of those goals 60 years ago today, with a mission called Gemini 4.   [AUDIO: 3, 2, 1, Ignition … Liftoff …] Astronauts James McDivitt and Ed White were scheduled to spend four days in space. That was longer than the first seven American missions combined. And White would make the first American spacewalk. He’d float outside the cabin for a few minutes, using a small “gun” of compressed air to move around. And three and a half hours after launch, it was time to get started: CAPCOM: Gemini 4, Hawaii capcom. We just had word from Houston, we’re ready to have you get out   whenever you’re ready. Okay, my feet are out. … Okay, I’m out. The spacewalk went well – very well. [WHITE: I feel like a million dollars!] In fact, it went so well that White didn’t want it to end. HOUSTON: The flight director says get back in!      McDIVITT: This is Jim, you got any message for us?      CAPCOM: Gemini 4, get back in!      McDIVITT: Okay… Actually working during a spacewalk turned out to be a lot harder than White had made it look. It took several more missions to work out the kinks. But the success of Gemini 4 helped make it possible for astronauts to walk on the Moon just four years later. Script by Damond Benningfield

If you step outside at dawn on June third of 2033, you’ll see the planet Venus standing due east – the brilliant “morning star.” But if you don’t want to wait that long to experience that beautiful view, then take a look at dawn tomorrow – Venus will be standing in the same spot in the sky. Not only that, it stands at that spot in the sky every eight years. In fact, anytime you see Venus – whether as the morning star or evening star – you can find it at that same spot eight years later. That’s because there’s a near-“resonance” in the orbital cycles of Earth and Venus. Venus completes 13 orbits around the Sun for every eight orbits that Earth makes. The ratio isn’t exact, but it’s quite close. Thanks to that, Venus follows five repeating cycles across our sky. It’s like the planet is a toy train on a looping, winding track. It hits every point along the track with every cycle. If you plot that motion from the perspective of Earth, it traces out a flowing pattern like five rose petals. The clockwork precision makes it easy to predict the entire sequence of Venus’s appearances. We know that it always remains in view in the morning sky for about 263 days, disappears for about 50 days, then moves into the evening sky. So if you miss the view of Venus tomorrow, or the next day, or the day after that, just mark it in your calendar – and look for it in the same location eight years later. Script by Damond Benningfield

The Moon has regular dates with the stars. It returns to the same position relative to the stars every 27 days and eight hours. As an example, the Moon cozied up to Regulus, the bright heart of the lion, on May 5th, and it does so again this evening – 27 days, eight hours later. This encounter is especially close as seen from the United States – the Moon and Regulus will appear to almost touch each other. That time span is known as the lunar sidereal period – “sidereal” meaning “related to the stars.” The planets have their own sidereal periods. Mars, for example, returns to the same point relative to the stars every 22 and a half months. Tonight, Mars is well to the lower right of Regulus, and looks like an orange star. It’ll return to almost the same position in April of 2027. The match won’t be exact because our viewing angle to the Red Planet changes a bit from year to year. The sidereal period is different from the period relative to the Sun – a difference caused by Earth’s own orbital motion. For the Moon, that period lasts 29 and a half days – the length of a cycle of phases. And for Mars, the Sun-related period is almost 26 months. That’s how long it takes Mars to return to the same angle from the Sun – part of the precise but sometimes confusing motions in the night sky. More about the motions of the planets tomorrow. Script by Damond Benningfield

To the more poetic among us, summer is a time of soft breezes, warm nights, and fireflies: The livin’ is easy, the breeze makes us feel fine, the warm Sun shines kindly upon us. But there’s less poetry in the summers on Mars – especially in the northern hemisphere, where summer began on Thursday. It stays cold, and the only fireflies are occasional meteors blazing through the night. Like the seasons on Earth, those on Mars are caused by the planet’s tilt on its axis. Northern summer begins when the north pole dips most directly toward the Sun. But Mars’s orbit is much more lopsided than Earth’s, so there’s a much greater change in the planet’s distance from the Sun. Mars is farthest from the Sun during northern summer. So the summer stays fairly cool. Summers and winters tend to be quiet times in the planet’s thin atmosphere. Big dust storms fire up in spring and fall, sometimes covering the whole planet. But they settle down by the start of summer. Mars does see more “dust devils” during summer – whirlwinds that can tower miles high. Northern summer will last for 178 Mars days – not giving way until the start of autumn exactly six months from now. Mars is close to the upper left of the Moon at nightfall, and looks like a fairly bright orange star. The true star Regulus is farther along that line. More about this lineup tomorrow. Script by Damond Benningfield

The United States plans to send astronauts to the Moon later in this decade, aiming toward a permanent lunar base. But experience shows that plans come and go. In fact, if all the plans for lunar exploration had actually come about, we’d be skittering all across the Moon today. In 1958, for example, the Air Force developed Project LUMAN, a comprehensive plan for human spaceflight. It would culminate with a single astronaut landing on the Moon. Later, the service developed another plan – LUMEX. It called for three astronauts to travel to the Moon using a giant new booster and a streamlined spaceship. The Army developed its own plan, involving a space station and other steps. All of those plans died – in part because human spaceflight was turned over to a new civilian agency: NASA. And NASA had its own false steps. It studied using its two-man Gemini spacecraft for lunar missions before settling on Apollo. And even then, some of its plans were scuttled; the final three Apollo missions were scrapped, in 1970. President George W. Bush proposed lunar missions as part of the Constellation program. It was nixed by President Obama. But some of its hardware has been kept for Artemis – which plans to send astronauts to the Moon in the next few years. Look for the Moon in the west at nightfall. The twin stars of Gemini stand to its lower right, with Mars to its upper left – another planned destination for human explorers. Script by Damond Benningfield

Globular clusters are the oldest members of the galaxy. They’re tight balls of hundreds of thousands of stars, most of which were born when the universe was no more than a couple of billion years old. Their most-massive stars have long since died. And most of the stars that remain are cool and faint. So a globular tends to be fairly quiet and calm. But that doesn’t mean that things don’t change. Consider Messier 13. It’s in Hercules, which is high in the east at nightfall. Under dark skies, the cluster is just visible to the unaided eye, looking like a faint, fuzzy star. The cluster is about 25,000 light-years away, and it contains up to half a million stars. But the stars at the edge of the cluster aren’t held as tightly as those in the middle. So the gravity of the rest of the galaxy can pull some of them away. In fact, astronomers have identified a few dozen stars that appear to be escapees from M13. But the cluster also can grab stars from the space around it. One especially young star probably became a member of the cluster that way. And stars inside the cluster can change. Some of them merge, forming bright, blue stars that look much younger. And stars die. M13’s brightest member is dying right now. It’s about as massive as the Sun, but it’s puffed up to dozens of times the Sun’s diameter. Soon, it’ll blow away its outer layers, leaving only its tiny, dead core – one more change in an ancient family of stars. Script by Damond Benningfield

Three of the four big moons of Jupiter appear to have something in common: oceans of liquid water below their crusts. For Europa, the ocean is considered a slam dunk. The case is also strong for Ganymede. But the case for the third moon, Callisto, is the weakest. Callisto is about 3,000 miles in diameter – bigger than our own moon. And it’s more heavily cratered than any other large body in the solar system. That indicates that the surface of Callisto is pretty much dead. But things might be different far below the surface. In the 1990s, the Galileo spacecraft flew near Callisto eight times. Its measurements of the magnetic field around the moon hinted that a salty ocean was sloshing around inside. But those observations also could be produced by an electrically charged layer of Callisto’s thin atmosphere. In a recent study, though, scientists looked at all of Galileo’s observations, and used computer models to understand them. The work suggested that there is an ocean. It could be dozens of miles deep. But it’s buried beneath an icy crust that could be hundreds of miles thick. Two spacecraft that are en route to Jupiter will fly close to Callisto many times. Their observations should tell us for sure whether an ocean is sloshing below Callisto’s battered surface. Jupiter stands below our moon in the early evening twilight. It looks like a bright star. Script by Damond Benningfield

If stars had trophy cases, Vega’s would be packed. The leading light of Lyra was the first star other than the Sun to have its picture taken, the first to have its spectrum taken, and the first with a published measurement of its distance. Vega is impressive in many ways. It’s more than twice the size and mass of the Sun, and about 50 times the Sun’s brightness. It’s encircled by a wide belt of dust, produced by collisions between big chunks of ice and rock. In about 12,000 years, it’ll serve as the Pole Star. And in about 200,000 years it’ll become the brightest star in the night sky. Vega first had its picture taken in 1850. In 1872, an astronomer took a picture of its spectrum, spreading its light into its individual wavelengths. A spectrum reveals a star’s composition, motion, and much more. In 1838, Russian astronomer Friedrich von Struve published Vega’s parallax – the first publication for any star. He plotted its position when Earth was on opposite sides of the Sun. That revealed a tiny shift against the background of more-distant objects. That shift revealed a distance of about 26 light-years – just one light-year off the modern measurement. Vega is low in the east-northeast at nightfall and climbs high overhead during the night. It’s the fifth-brightest star in the night sky, so you can’t miss it – a beautiful star with a case full of trophies. Script by Damond Benningfield

One of the major beauties of the summer sky dangles in the northeast this evening like a piece of cosmic jewelry – the constellation Lyra. Its brightest star is Vega – the fifth-brightest star in the night sky. It sparkles like the diamond stud in an earring. The rest of Lyra hangs to its lower right like the rest of the earring. It forms a parallelogram – a slanted rectangle. Under fairly dark skies, it’s easy to see. Lyra represents a lyre – a small harp. In skylore, it was sometimes shown being held by a large bird – an eagle or vulture. In fact, the name “Vega” comes from an Arabic phrase that means “the falling eagle.” But mainly the lyre was associated with the story of Orpheus. His music was legendary. When he accompanied Jason and the Argonauts, his playing silenced the Sirens – evil creatures who lured sailors to their doom. Orpheus married Eurydice. But she was bitten by a snake and died. Orpheus begged Hades, the god of the underworld, to let Eurydice return to him. His music was so beautiful that Hades agreed. But there was one condition: Orpheus couldn’t look back until they were outside. But he couldn’t resist – he looked too soon, and Eurydice vanished into the underworld forever. Orpheus was heart-broken. He roamed aimlessly across the countryside, playing sad but beautiful music on his lyre – an instrument commemorated in the stars. We’ll have more about Vega tomorrow. Script by Damond Benningfield

The names of the stars are a cultural mash-up. The names come from Greek, Latin, Arabic, and other cultures. And some names combine words from different languages. Two examples are the stars Tania Borealis and Tania Australis. “Tania” comes from an Arabic phrase that means “the second.” Borealis and Australis come from Latin, and mean northern and southern. Combined, the stars represent the second leap of the gazelle – a bit of skylore from Arabia. Skywatchers there saw three close pairs of stars as the leaps of a gazelle. All three pairs are at the edge of the modern constellation Ursa Major, the great bear. The “Tanias” are above the stars that form the outer edge of the dipper’s bowl. Tania Borealis is a single star that’s a good bit bigger, brighter, and heavier than the Sun. It’s at the end of the prime phase of life, so it’s undergoing big changes in its core. That’s causing its outer layers to begin to puff up to giant proportions. Tania Australis is a binary – two stars bound together by their mutual gravitational pull. One of the stars is similar to the Sun. The other is more than six times the Sun’s mass, and it’s already reached the “giant” phase of life. It’s puffed up to about 75 times the Sun’s diameter, and it shines about a thousand times brighter. So Tania Australis looks a bit more impressive than its northern cousin – the brighter half of the second leap of the gazelle. Script by Damond Benningfield

A gazelle leaps past the feet of the great bear. In ancient skylore, in fact, it made three leaps – each marked by a pair of stars. The stars that mark the first jump are known as Alula Borealis and Alula Australis – the northern and southern first leaps. As night falls this evening, they’re high in the northwest. They’re far to the left of the Big Dipper, which has the most prominent stars of the great bear. The “alulas” are close together, so they resemble a pair of eyes. Alula Australis holds an important distinction in the history of astronomy. A telescope reveals it’s a “double” star – two stars that are close together. By measuring the motions of the stars, in the late 18th century, astronomer William Herschel showed that they’re bound to each other. That made the system the first confirmed binary – two stars that move through space together, tied by their mutual gravitational pull. A few decades later, it became the first binary to have its orbit accurately measured. The stars orbit each other once every 60 years, at an average distance of more than 20 times the distance from Earth to the Sun. In more modern times, astronomers found that both stars are binaries on their own – each has a small, faint companion in a tight orbit. So the first leap of the gazelle consists of at least four stars, leaping through the galaxy as a family. We’ll talk about the second leap tomorrow. Script by Damond Benningfield

About 44 lightning bolts flash through the skies of Earth every second. And for a while, it seemed there might be more flashes than that on Venus. Telescopes on Earth and spacecraft in orbit saw flashes of light in the planet’s clouds, or heard the sounds of lightning in the planet’s radio waves. One estimate said Venus could see several times more lightning bolts than Earth. But studies in recent years have suggested that lightning on Venus might be quite rare. Venus has a much thicker atmosphere than Earth does, topped by clouds of sulfuric acid. But there’s very little water vapor in the clouds. And water is a key ingredient for lightning on Earth and other worlds where it’s been confirmed. So that led to some skepticism about claims of lightning on Venus from early on. A Sun-watching spacecraft has swung close to Venus several times. It’s listened for radio waves like those produced by lightning on Earth. It found them. But they were headed in the wrong direction – toward the ground, not into space, as they are on Earth. And a Venus orbiter has spent hundreds of hours looking for lightning flashes, but hasn’t seen a thing. In fact, one recent study said some of the flashes seen from Earth might really be meteors burning up in Venus’s atmosphere. So lightning might be rare on our neighboring planet. Venus is the bright “morning star.” Tomorrow, it’s close to the crescent Moon. Script by Damond Benningfield

If you ever want to chat with someone on another planet, you better have a lot of patience. It takes a long time for a message from Earth to reach another world, and just as long for the reply to reach Earth. That’s because radio waves travel at the speed of light. And although light is pretty swift, its speed is limited – 670 million miles per hour. Given the scale of the solar system, that means there’s a long pause between halves of a conversation. Consider the planets that flank the Moon at dawn tomorrow: brilliant Venus to the lower left of the Moon, and fainter Saturn to the upper right. Right now, Venus is more than 58 million miles away. At that distance, it would take a radio signal from Earth about five and a quarter minutes to get there – a round-trip time of 10 and a half minutes. Saturn is about 930 million miles away. So the round-trip travel time is about two hours and 45 minutes. That’s a big concern for the folks who send probes to these and other planets. Despite what you might see in sci-fi movies and TV shows, there’s no way to have a real-time conversation. So spacecraft are programmed to do much of their work without direct help from Earth. And if they encounter a problem, they shut down most of their systems and place a call for help – then settle in for the long wait to hear from home. More about the Moon and Venus tomorrow. Script by Damond Benningfield

A 900-mile-wide, two-toned walnut orbits the planet Saturn. It’s Saturn’s third-largest moon, and definitely the most eye-catching. One hemisphere is as dark as coal, while the other is as bright as sea ice. And a mountain ridge wraps around the equator, making it look like a walnut. Iapetus was discovered in 1671. And right away, astronomers realized there was something odd about it. It was easy to see when it was on one side of Saturn, but invisible on the other. Today, we know why that’s the case: the planet’s leading hemisphere is 10 to 20 times brighter than the trailing hemisphere. The leading idea says that long ago, the darker side was pelted by dust and rocks blasted off some smaller moons. The darker material trapped the Sun’s heat, vaporizing ices. The vapor drifted to the other side, where it froze, making that side bright. And that process continues today – making Iapetus the “yin and yang” of moons. The ridge around the equator is about six miles high. It might have formed long ago when Iapetus rotated much faster than it does today. Or it might be the remains of a ring that collapsed onto the surface – making Iapetus look like a walnut. Saturn appears quite close to our own Moon at dawn tomorrow. It looks like a bright star to the lower left of the Moon. The much-brighter planet Venus is farther to the lower left. More about this morning lineup tomorrow. Script by Damond Benningfield

For the most part, black holes come in two varieties: small and jumbo. The small ones are the remnants of dead stars. They range from a few to about a hundred times the mass of the Sun. The jumbos inhabit the hearts of galaxies. They range from about a hundred thousand to several billion times the Sun’s mass. But there just isn’t much in the middle. In fact, astronomers have logged only a few dozen medium-sized black holes. And many of those are controversial – they’re hard to confirm. Most of them are in other galaxies, so it’s hard to see their influence on the stars and gas around them. One recent study may have added to the tally. Using observations designed to study dark energy, scientists said they discovered about 300 medium-sized black holes. About 70 of them inhabit the centers of small galaxies. Those black holes are gobbling gas and dust around them, making them brighter and easier to find. Theory says there should be many more black holes in size “medium.” They may be the remnants of the ultra-massive stars that populated the early universe. Or they may have formed when dense clumps of gas collapsed under their own gravity. Either way, it’s possible that such black holes were the “seeds” from which the jumbo black holes grew. For now, the search continues for these hard-to-find medium-sized black holes. Script by Damond Benningfield

The closest galaxy we can see other than our own Milky Way may be inside the Milky Way. Its outer precincts have been stripped away, leaving only its core – a tight ball of 10 million stars. And a rare type of black hole appears to lurk in its middle. Omega Centauri rolls low across the south during the night. The view is better from the southern half of the country. To the eye alone, it looks like a fuzzy star. Omega Centauri is classified as a globular cluster – a family of very old stars. It’s the biggest one in the galaxy. But it probably wasn’t born in the Milky Way. Instead, it began as a separate galaxy. But it was reeled in by the Milky Way’s gravity, which also pulled away most of its stars. Only the stars in the galaxy’s core stuck together. An intermediate-mass black hole appears to inhabit the center of the cluster. Such beasties are rare. Most black holes are either no more than about a hundred times the mass of the Sun, or a few hundred thousand times the Sun’s mass or more. A study a couple of decades ago reported a possible black hole in Omega Centauri weighing 40,000 times the Sun’s mass. Later work suggested that number was too high. The most recent estimate was compiled from 20 years of observations by Hubble Space Telescope. It puts the black hole at about 8,000 times the Sun’s mass – a rare black hole in the remnant of a dead galaxy. More about mid-sized black holes tomorrow. Script by Damond Benningfield

Mighty Hercules stands well up in the east and northeast as night falls. His most prominent feature is the Keystone, a lopsided square of stars that represents his body. But the constellation’s brightest star isn’t part of the Keystone. Instead, it represents the entire strongman: Its name, Kornephoros, comes from a Greek word that means “the club bearer” – Hercules himself. Like many of the stars in the galaxy, there’s more to Kornephoros than meets the eye: It consists of two stars, not one. One star is smaller and fainter than the Sun, so it’s not visible to the eye alone. The visible star, on the other hand, is about three times the mass of the Sun, almost 20 times the Sun’s diameter, and 150 times its brightness. So the star is an easy target even though it’s about 140 light-years away. The star is nearing the end of its life. It’s probably consumed the hydrogen fuel in its core, converting it to helium. That’s caused the core to get smaller and hotter. The extra radiation pushes on its outer layers, causing them to puff up to giant proportions. Today, Kornephoros is fusing the helium to make carbon and oxygen. Eventually, that process will end. The star will lose its outer layers, leaving only its dead core – and the “club bearer” will vanish from sight. For now, though, look for it due east at nightfall, halfway up the sky – the first modestly bright star to the right of the Keystone. Script by Damond Benningfield

A pretty semicircle of stars crowns the sky on spring and summer nights: Corona Borealis, the northern crown. It’s in the east as night falls now, and stands high overhead a few hours later. In a couple of months, it’ll be overhead at nightfall. Most of the semicircle isn’t very bright – you need pretty dark skies to see it. It stands out because of the tight pattern, with a fairly bright star at the center: Alphecca, “the bright one.” Alphecca is really a binary – two stars locked in a gravitational embrace. The heavier of them is about three times as massive as the Sun, thousands of degrees hotter, and dozens of times brighter. Its companion is a little smaller and fainter than the Sun. The stars are quite close together – an average of about half the distance between the Sun and its closest planet, Mercury. The stars orbit each other once every 17 and a half days. And they’re lined up in such a way that we see the fainter star pass in front of the brighter one – an eclipse. When that happens, Alphecca dims by a few percent. That’s not enough for most of us to notice with the eye alone, but it’s an easy catch for astronomical instruments. Instruments also see a disk of debris around the stars. It extends billions of miles into space. It consists mainly of small grains of dust – material left over from the formation of Alphecca itself. We’ll talk about a pair of stars in Hercules tomorrow. Script by Damond Benningfield

Hubble Space Telescope had many “parents” – people who conceived it, lobbied for it, designed it, and mapped out its science mission. But none was more important than Nancy Grace Roman. She served as NASA’s first chief astronomer, and later as director of one of its field centers. She pushed, prodded, and cajoled for the telescope for decades. And once it was approved, she helped get it running. Roman was born 100 years ago today, in Nashville. In sixth grade, she founded her school’s first astronomy club. A year later, she decided to become an astronomer. Despite discouragement from teachers, she stuck with it. She earned her Ph.D., from the University of Chicago, in 1949. Over the next few years she studied the stars, using telescopes at McDonald Observatory and elsewhere. Academia didn’t offer much opportunity for women at the time, so Roman went into government work. And soon after NASA was established, she was hired as chief astronomer. Among other things, she led the development of the first space telescopes – one series to watch the Sun, another to study the stars. Roman died on Christmas Day in 2018. But her legacy is far from over. NASA’s next big space telescope will hunt for planets in other star systems, probe the nature of dark energy, plot the evolution of the universe, and more. The telescope is scheduled for launch in two years: the Nancy Grace Roman Space Telescope. Script by Damond Benningfield

For the most part, the star cluster NGC 2281 has escaped the attention of astronomers. It hasn’t been studied in a lot of depth over the years. So many of its details haven’t really been locked down. So far, astronomers have cataloged more than 200 stars in the cluster. And they’ve ruled out many more stars that happen to line up in the same direction. That makes NGC 2281 a fairly puny cluster. The cluster’s distance is a bit uncertain as well. Measurements have been getting better in recent years, thanks in part to the Gaia space telescope. It’s obtained precise details on several of the stars in the cluster, including their distance. Those observations put NGC 2281 at more than 1700 light-years. And its age is still debated, too. Estimates in recent years have ranged from about 275 million to 630 million years. Various studies have used different techniques to plot the age. That includes the types of stars found in the cluster, the number of dead stars, and even how fast the Sun-like stars in the cluster spin; stars slow down as they age. NGC 2281 is in Auriga the charioteer, in the west-northwest as night falls. The “twins” of Gemini stand to its upper left, with the brilliant star Capella farther to its lower right. Under clear, dark skies, it’s visible to the unaided eye as a hazy patch of light – a star cluster that we’re still getting to know. Script by Damond Benningfield

The “halo” that surrounds the Milky Way Galaxy is dark but heavy. It’s much more massive than the galaxy’s bright disk, but we don’t see much there. So the halo must be filled with dark matter. It produces no detectable energy, but it reveals its presence through its gravitational pull on the matter we can see. The leading idea says dark matter consists of some type of exotic particle. But efforts to find such particles have come up empty. Astronomers have also looked to see if the dark matter might consist of MACHOs – massive compact halo objects. The list of candidates includes faint stars, dead stars, black holes, free-floating planets, and brown dwarfs. Such objects are extremely faint. But they can sometimes brighten – not directly, but by magnifying the light of stars behind them. The technique is known as gravitational lensing. When one massive body passes in front of another, it causes the background object to get much brighter. The flare-up can last from hours to months. How long it lasts, and how much the background star brightens, reveals details about the lensing object. And that reveals the type of object. Searches for gravitational lenses have found many planets, faint stars, and even the first “rogue” black hole – one that couldn’t be seen any other way. But there just aren’t enough MACHOs to account for more than a small fraction of the dark matter – leaving us in the dark about its nature. Script by Damond Benningfield

The human eye is amazing. It can focus on objects near and far, provide a three-dimensional look at the world, and see under both brilliant sunlight and the faint glow of the stars. It also sees all the colors of the rainbow – from red and orange to blue and violet. Yet there’s a lot more that the eye can’t see – wavelengths that are beyond its range. That means we’re missing much of what the universe is showing us. Consider Antares, the heart of the scorpion. The star is just a whisker away from the Moon as they climb into view this evening. Antares is one of the brightest pinpoints in the night sky. And it shines with a distinctly orange hue. But there’s a lot more to it than that. For one thing, Antares consists of two stars, not one. The one we see is a supergiant – many times the Sun’s mass, and hundreds of times its diameter. At visible wavelengths, it shines about 10,000 times brighter than the Sun, with a distinctly orange color. But the star is much cooler than the Sun. Such stars produce most of their energy in the infrared – wavelengths too long for the human eye. So when you add that in, Antares is about a hundred thousand times the Sun’s brightness. The other star of Antares is much hotter than the Sun. So most of its light is in the ultraviolet – wavelengths that are too short for the eye. So it is about three thousand times the Sun’s brightness – much more than the eye can see. Script by Damond Benningfield

Our planet’s north magnetic pole is on a journey across the top of the world. But it’s slowing down. Over the past five years, it’s put on the brakes – its position has changed much more slowly than over the previous couple of decades. Earth’s magnetic field acts like a giant bar magnet, with north and south poles. The poles aren’t tied to the geographic poles – they wander. The north magnetic pole was discovered in 1831. At the time, it was centered over northwestern Canada. It moved farther south, then made a big turn, toward Siberia. In all, it’s moved almost 700 miles since it was discovered. For a couple of decades, it was moving at more than 30 miles per year. More recently, though, it’s slowed to about 22 miles a year – the biggest slowdown ever recorded. Scientists are trying to understand why. The magnetic field is generated by motions of molten rock in Earth’s outer core. Those motions produce electric currents, which create the magnetic field. So the changing position and rate of motion are telling us something about what’s going on deep inside our planet. The change in the magnetic pole has important practical implications as well as scientific ones. GPS, aircraft, the military, and others use magnetic north for navigation. So maps of Earth’s magnetic field are updated every few years to show the change in the pole’s location – keeping everyone headed in the right direction. Script by Damond Benningfield

The full Moon achieves a sort of celestial balance tonight. It’s passing across Libra, the balance scales – a symbol of justice. But the proper names of the constellation’s brightest stars have nothing to do with balance, justice, or anything similar. Instead, the names mean “the claws” – of nearby Scorpius, the scorpion. Originally, the stars did belong to Scorpius. But thousands of years ago, they were severed from the scorpion and placed in a new constellation. As night falls, one of the claws stands to the upper left of the Moon. Called Zubenelgenubi, it represents the southern claw. It’s the second-brightest star of Libra, and it’s about 75 light-years away. Like many of the stars in the night sky, Zubenelgenubi is deceiving. To the eye alone, it looks like a single point of light. Scan it with binoculars, though, and you’ll see two stars. They appear to be moving through space together, so they might be orbiting each other. But they’re so far apart that it takes the light from each star a month to reach the other one. At that separation, they might not be held together by gravity – their close appearance might be just a coincidence. Each of the two stars is actually a binary in its own right. In both cases, the stars are so close together that even giant telescopes can’t see them as individual stars. But we see the “fingerprints” of two stars in the light from each half of the southern claw. Script by Damond Benningfield

As World War II wound to an end, President Franklin Roosevelt asked his top scientific advisor a question: How could the type of research that helped win the war be applied to peacetime? The advisor suggested a new agency to support basic research at colleges and universities. It took a few years to work out the details. But 75 years ago today, President Harry Truman signed the law establishing that agency: the National Science Foundation. Over the decades, its mission has expanded into many fields, from chemistry and physics to computers and materials science. The list also includes astronomy. NSF established the first national observatories in 1956 – optical telescopes in Arizona, and radio telescopes in West Virginia. Today, NSF-supported facilities span the globe. They include observatories that no one was even dreaming of when the agency started. They hunt for the ghostly particles known as neutrinos, and listen for gravitational waves from merging black holes and neutron stars. NSF also is a partner in the Vera Rubin Observatory, which is scheduled to take its first peek at the universe this summer. Its giant telescope will scan a wide slice of the sky every night. It will discover exploding stars, asteroids, and other objects. It will map the Milky Way Galaxy. And it’ll provide new information about dark energy and dark matter – basic research that will teach us much more about the universe. Script by Damond Benningfield

The star Spica, which is quite close to the Moon tonight, is quite different from the Sun. It consists of two stars, not one. Both stars are many times bigger and heavier than the Sun. And their surfaces are tens of thousands of degrees hotter, so the stars shine blue-white. On the other hand, the Sun and Spica are made of almost exactly the same ingredients: mainly hydrogen and helium, with only a smattering of heavier elements. That composition was figured out by an astronomer who was born 125 years ago tomorrow, in England. Cecilia Payne caught the astronomy bug when she saw a lecture by Arthur Eddington, one of the world’s leading astronomers. She started her education in England, then finished in the United States. She earned a Ph.D. in 1925. And her doctoral thesis shook up the field. Decades later, in fact, Otto Struve, the first director of McDonald Observatory, called it the most brilliant thesis ever written in the field. Astronomers already had the techniques for measuring what stars are made of. Their work led them to believe that stars contain the same mixture of elements as Earth. But Payne used a new way to analyze the readings, taking into account the charge of atoms. She concluded that stars were made mainly of hydrogen and helium – elements formed in the Big Bang. By a few years later, just about everyone accepted her analysis – completely changing our concept of the stars. Script by Damond Benningfield

The surface of the Sun is like a pot of boiling water. Millions of bubbles of hot gas churn across it, constantly rising and falling. But the bubbles are a little bigger than those on your stovetop. The bubbles are known as granules. They form as energy from deep inside the Sun works its way to the surface. That heats the gas in the Sun’s top layer, forming bubbles. As they reach the surface, their gas cools and drops back into the Sun. This non-stop activity creates an easy-to-see pattern of bright blobs – the hot gas – with dark lanes between them – the cooler gas. The size of the granules varies from about a hundred miles to more than a thousand – big enough to swallow Texas. And each granule lasts for no more than about 20 minutes. A recent study said the granulation changes a bit during the Sun’s 11-year cycle of magnetic activity. Just after the peak of the cycle, there are slightly more granules than average, but they’re a little smaller than average. Other stars are so far away that we can’t see the granulation on most of them. But several types of observations confirm that they, too, are boiling away. Astronomers have seen granulation on a few stars. The stars are much bigger than the Sun. And they’re late in life, so they’re undergoing big changes. The granules on those stars are tens of millions of miles across – dozens of times the diameter of the Sun – giant bubbles of hot gas on giant stars. Script by Damond Benningfield

The Gaia spacecraft took its final look at the stars in January. But its work is far from over. Its observations will be producing new discoveries for decades. Above Earth’s blurring atmosphere, the space telescope kept a sharp eye on the heavens for more than a decade. It studied about two billion objects – mostly stars. It measured their temperature, composition, and motion. And it plotted their positions with amazing precision. That’s allowed astronomers to produce the best 3-D maps of the Milky Way Galaxy to date – by far. Those maps have helped plot the origins of many stars – the remains of star clusters or even small galaxies pulled in by the Milky Way. And that’s revealed a lot more about the history of the entire galaxy. Gaia also looked at other galaxies, at asteroids and comets in the solar system, and many other objects. It even helped reveal a couple of planets in other star systems. The craft ran out of the gas it used to keep its telescope on target, bringing its mission to an end. But it takes a lot of time to process Gaia’s observations and release them for study. There have been three big batches so far, which have yielded more than 13,000 scientific papers. The next big release is scheduled for late next year. And the final release – everything Gaia saw and reported – won’t be ready until late 2030 at the earliest – a treasure trove that astronomers will be poking through for decades. Script by Damond Benningfield

The gusty winds of spring make it a good season for flying a kite. But you might not want to try it on the planet Wasp-127 b – it would be hard to hang on. Winds high above the surface blow at an astounding 20,000 miles per hour – a hundred times faster than winds in the strongest category five hurricanes on Earth. The star – Wasp-127 – is a lot like the Sun. But the planet isn’t much like any planet in the solar system. It’s much wider than Jupiter, the largest planet. But it’s only one-sixth of Jupiter’s mass. That makes it one of the “puffiest” planets yet seen. Wasp-127 b was discovered because it passes in front of its parent star every four days. As it does so, starlight filters through the atmosphere. Astronomers use that effect to learn something about the atmosphere. Recent observations revealed that material in the upper atmosphere is moving extremely fast – blown by the fastest winds yet seen on any planet. The observations also suggested that there’s a big temperature difference between the dawn and evening skies – more than 300 degrees Fahrenheit – one more reason the planet isn’t a good place to fly a kite. The Wasp-127 system is in the constellation Sextans, the sextant. This evening, it’s well to the lower right of the Moon. But the system is more than 500 light-years away, so the star is too faint to see without a telescope. Script by Damond Benningfield

Over the millennia, every culture has named the bright stars. The names represented characters from mythology, things from the natural world, human traits and values, and more. Different cultures seldom agreed on what to call an individual star. But one exception seems to be Regulus, the brightest star of Leo. Just about everybody saw the star as a symbol of strength and power. The name “Regulus” means “the little king.” The name made its debut in the early 16th century – translated from the Greek name with the same meaning. Other cultures held the star in similar regard – as a king, a hero, or as the center – an especially important marker in the night sky. It’s not hard to see why Regulus was held in such high esteem. It’s quite bright – only a couple of dozen stars and planets outshine it, and many of those just barely top it. And Regulus lies near the ecliptic – the Sun’s path across the sky. Any star close to that path has always received special attention. And there aren’t many bright stars close to Regulus – especially along the ecliptic. So Regulus has held a lofty position in the sky stories of many cultures – a “little king” at the heart of the lion. Regulus appears quite near the Moon as night falls this evening, and a bit farther from the Moon as they set in the wee hours of the morning. Although it loses a bit of its luster in the glare of the Moon, the star is always a beautiful sight. Script by Damond Benningfield

No one has seen Comet Halley in decades. Even so, it’s reminding us of its presence about now. That’s because it’s responsible for the Eta Aquarid meteor shower. The shower is predicted to reach its peak tomorrow night, with top rates of about 40 or 50 meteors per hour. A meteor shower occurs when Earth passes through the orbital path of a comet. As a comet nears the Sun, some of the ice at its surface vaporizes in the heat. That releases small bits of rock and dust. Over time, this “comet dust” spreads out along the comet’s orbit. When Earth intersects the orbit, some of the debris slams into the atmosphere at tens of thousands of miles per hour – forming the glowing streaks known as meteors. The Eta Aquarids are one of two showers that are caused by Halley. The other takes place in October. Our planet passes a little deeper into the debris field in May, so this shower is better. Yet we’re a long way from the center of Halley’s trail – catching the fringe of a trail of comet dust. The shower is in better view from the southern half of the country. That’s because the point at which the meteors appear to “rain” into the atmosphere stays low in the south. To see the Eta Aquarids, find a dark, safe skywatching site, away from city lights. The best view comes in the wee hours of the morning. The Moon will be out of the way then, making it easier to see the “shooting stars” from Halley’s Comet. Script by Damond Benningfield

The Moon and Mars are flirting with danger – they’re sneaking up on the Beehive star cluster, in the constellation Cancer. The cluster doesn’t have much of a “sting,” though – it’s about 600 light-years away. The Beehive contains about a thousand stars, which are maybe 700 million years old – fairly young in astronomical terms. That means the Beehive maintains a mixture of stars of different masses. Its heaviest stars have burned out, leaving only their dead cores. About two-thirds of the remaining stars are red dwarfs – cool, faint embers only a fraction of the mass of the Sun. About a third are similar to the Sun. And about two percent are heavier than the Sun. Because more-massive stars burn through their nuclear fuel more quickly, those stars will expire first. The cluster’s brightest star is Epsilon Cancri. Although it looks like a single point of light, instruments reveal that it consists of at least three stars. All three are more than twice as massive as the Sun, so they’re nearing the end of the prime phase of life. Soon, they’ll puff up to giant proportions. After that, they’ll blow away their outer layers, exposing their dead cores – and the Beehive will lose some of its luster. The Beehive is close to the lower left of the Moon at nightfall, and is an easy target for binoculars. Mars looks like an orange star below the Moon. It’ll slip past the cluster over the next couple of days. Script by Damond Benningfield

The universe can be frustrating. Roughly two-thirds of everything in the universe appears to consist of dark energy. Despite decades of study, though, scientists haven’t been able to explain what dark energy is. Astronomers discovered dark energy by studying a type of supernova – exploding stars. The supernovas brighten and fade in a predictable way. That allows astronomers to measure their distance and their motion away from us. Stars that are farther were moving away faster than expected. That suggested that something was causing the universe to expand faster over time: dark energy. But a recent study said that dark energy might not exist. Instead, the researchers proposed a new model to explain what we see, called timescape. The model notes that matter clumps together in clusters of galaxies, with huge “voids” between them. Time passes more slowly in the presence of stronger gravity – like that exerted in the denser regions. So the voids, with less gravity, could be billions of years older than the clusters – creating “bubbles” of spacetime. If that’s correct, then it would be tough to know just when the supernovas in different parts of the universe exploded. And that makes it tough to know how fast they’re moving away from us. So the study says we don’t need dark energy to explain what we see in the universe. But there’s still a lot of work to be done to understand dark energy – including whether it even exists. Script by Damond Benningfield

The modern western calendar tells us that summer arrives in the northern hemisphere this year on June 20th – the summer solstice. It’s the longest day of the year, and the Sun stands farthest north for the year as well. In ages past, many calendars had a less direct link to the solstices and equinoxes. The seasons began not on these dates, but about halfway between them. Such dates are known as “cross-quarter” days. And in the calendars of the ancient British Isles, one of those days was commemorated on May 1st. In Ireland and Scotland it was known as Beltane; in other regions, it was May Day. The rituals of Beltane celebrated the end of the cold, dark time of year and the beginning of the longer, warmer days of summer. The centerpiece of Beltane was a village bonfire – or perhaps two bonfires. The fires themselves chased away the darkness and ushered in the light of summer. The flames and smoke were thought to have special protective powers, so villagers doused the fires in their homes, then relit them using a torch from the bonfire. They also paraded their livestock past the fires on the way to their summer fields – providing a bit of good luck for the start of the summer growing season. These rituals were part of a deep connection to the cycles of nature, and especially the Sun – which warms and lights the summer no matter when the season kicks off. Tomorrow: different clocks for different flocks. Script by Damond Benningfield

Telescope domes are designed to keep the telescopes inside safe and on-target. But just because they’re practical doesn’t mean they can’t be beautiful. That’s especially true of some built in the 1930s. They were influenced by the design style that was all the rage – known today as art deco. The event that popularized art deco began 100 years ago this week – the International Exhibition of Decorative Arts and Modern Industries, in Paris. It was a showcase for French design in architecture, art, furniture, clothing, and other fields. Most countries participated. The only restriction: Everything had to be modern. The exhibition inspired a design wave across the United States. Popular examples include the Empire State Building and Chrysler Building in New York, along with trains, airplanes, cars, consumer goods, and more. Astronomy got into the act as well. The best-known example is Griffith Observatory, in Hollywood. Its domes and grounds have been featured in dozens of movies and TV shows. The domes of Palomar Observatory feature art-deco design as well, including the one that houses the 200-inch telescope – the largest in the world for decades. And no list is complete without our own McDonald Observatory. Its original dome was dedicated in 1939. It housed not only the observatory’s 82-inch telescope, but also labs, offices, and living space for the astronomers – all executed in beautiful art deco style. Script by Damond Benningfield

Until about 30 years ago, Jupiter was the king of the planets – bigger and heavier than any other known planet. Today, it’s not even in the top 500. It’s still the giant of our own solar system – it’s more massive than all the other planets and moons combined. But hundreds of planets in other star systems outrank it. The total number of confirmed exo-planets is up to about 6,000. They range from chunks of rock about as massive as the Moon to super-planets up to about 80 times Jupiter’s mass. Such giants are much easier to find than smaller worlds. Astronomers find most exoplanets in a couple of ways. One is to watch as a star fades a bit as a planet passes in front of it. Larger planets block more starlight, producing a bigger dip. The other way is to measure a tiny shift in a star’s light caused by the gravitational pull of an orbiting planet. Heavier planets exert a stronger pull, making them easier to find. Many of the “super Jupiters” are especially close to their parent stars. So these are the easiest planets to find. Over the years, though, the list of such planets in more-distant orbits has grown as well – bumping Jupiter farther from his throne as “king” of the planets. Jupiter is still a giant presence in our sky. It looks like a brilliant star. And it’s close to the Moon the next couple of nights – to the upper left of the Moon tonight, and a little closer below the Moon tomorrow night. Script by Damond Benningfield

Trillions of icy bodies mark the edge of the solar system. They form a shell that extends one or two light-years from the Sun in every direction. A passing star may sometimes give some of them a nudge toward the Sun. When they get here, they become comets – visitors from the icy deep. That distant region is known as the Oort Cloud. It’s named for Dutch astronomer Jan Oort, who was born 125 years ago today. He proposed the existence of the cloud in 1950. And today, that’s his best-known accomplishment. Yet it’s far from his most important work. Early in his career, he confirmed that the Milky Way is a wide, flat, spinning disk. And he showed that, instead of inhabiting the center of the galaxy, the solar system is in the hinterlands – many thousands of light-years outside the heart. Oort spent most of his career at Leiden University in the Netherlands, including decades as director of Leiden Observatory. When Germany invaded the country, though, he left his post instead of working with the Nazis. When he returned, after World War II, he became a pioneer in the new field of radio astronomy. He mapped giant clouds of gas and dust throughout the galaxy. Their distribution provided even more proof of his picture of the Milky Way. Oort continued his research until shortly before his death, in 1992. Scientists have named quite a few things in his honor, including an asteroid – and the icy shell known as the Oort Cloud. Script by Damond Benningfield

Dark spots sometimes dot the surface of the Sun – magnetic storms that can last for days or weeks. But the storms on other stars can make those on the Sun look puny. They can be so monstrous that they can change the star’s brightness by quite a bit. An example is one of the stars of Cor Caroli – the Heart of Charles. As seen by the eye alone, the star is the leading light of Canes Venatici, the hunting dogs. It’s to the right of the handle of the Big Dipper as night falls, and wheels above the dipper later on. But a closer look shows that Cor Caroli consists of two stars in a wide orbit around one other. One of the stars is about half again as massive as the Sun, and several times brighter. The other is about three times the Sun’s mass, and more than a hundred times its brightness. But over a period of about five and a half days, the heavier star’s brightness varies by about 15 percent. And that’s because of the starspots. The star’s magnetic field is more than a thousand times stronger than the Sun’s. That produces giant spots – far bigger than anything ever seen on the Sun. The spots are thousands of degrees cooler than the surrounding gas. The combination makes them darker than the rest of the surface. As the star rotates, the spots move in and out of view, causing the star to get fainter and brighter – a big “flutter” for the Heart of Charles. Tomorrow: an astronomer with a “cloudy” name. Script by Damond Benningfield

The stars Kochab and Pherkad serve several roles. They’re part of the body of Ursa Minor, the little bear. They form the outer edge of the bowl of the Little Dipper. And they’re “guardians of the pole” – they circle around Polaris, the star that marks the north celestial pole. Both stars are giants – they’ve puffed up at the end of the prime phase of life. Kochab is about 50 times the Sun’s diameter, and 450 times its brightness. Pherkad looks fainter than Kochab, but only because it’s almost four times farther. In reality, it’s more than twice as bright. The stars are so big and bright because they’ve exhausted their original supply of nuclear fuel. That’s triggered changes in the cores of the stars that have caused them to puff up. In ages past, both stars were much closer to the pole than they are today. In fact, Kochab was the closest bright star to the pole for a millennium. It was the best pole star about 3100 years ago. But it wasn’t nearly as good a marker as Polaris – it never got closer than about seven degrees, which is almost the width of a fist held at arm’s length. Thanks to an effect called precession, it’s moved away from the pole. So Kochab and Pherkad serve as guardians of the pole. The stars stand to the right of Polaris at nightfall, and wheel high above the Pole Star later on. Kochab is the second-brightest star of the little bear, shining just a touch fainter than Polaris. Script by Damond Benningfield

A Chinese spacecraft that’s scheduled for launch as early as next month has a double destination: a “quasi-moon” of Earth and an asteroid that acts like a comet. The first destination for Tianwen-2 is an asteroid, Kamo’oalewa. It’s a chunk of rock no more than the length of two or three football fields. What makes it intriguing is that it weaves around the Sun in a pattern that makes it look like a satellite of Earth. The asteroid spends half of its time farther from the Sun than Earth is, the other half closer to the Sun. Seen from Earth, it appears to loop around our planet – like a moon. Some research suggests it was a chunk of the Moon that was blasted into space by a big impact. Tianwen-2 is scheduled to arrive at Kamo’oalewa next year. It’ll spend a year traveling along with the asteroid. It’ll drop off a small lander and rover, and collect a few ounces of rocks and dirt. The craft will swing by Earth to drop off the samples, then journey to 311P Panstarrs. The object is a third of a mile wide, and orbits the Sun at about twice Earth’s distance. Observations reveal that Panstarrs is rocky, like an asteroid. But soon after it was discovered it sprouted several long tails, so it was classified as a comet. It may be a loosely bound pile of rocks and dust. If so, it may sometimes lose some of the dust, and sunlight then pushes it away – giving this asteroid the tails of a comet. Script by Damond Benningfield

A beautiful triangle decorates the dawn sky tomorrow. Two of its points are easy to see: the crescent Moon and the planet Venus, the “morning star.” The final point is a bit tougher: the planet Saturn, to the upper right of the Moon. It’s just half of one percent as bright as Venus, but its proximity to the brighter bodies will help it stand out. Saturn is about as faint as it ever looks right now. One reason is that it’s just emerging from behind the Sun, so it’s about as far as it ever gets from Earth – more than 950 million miles. The other reason is our view of Saturn’s rings. The rings span almost the distance from Earth to the Moon, and they’re made mainly of small bits of ice, which reflect a lot of sunlight. But the angle at which we see the rings changes – a result of Saturn’s changing seasons. Saturn is tilted at about the same angle as Earth. At the solstices, one of Saturn’s poles dips toward the Sun, so we see the rings at their best angle. That makes the planet especially bright. At the equinoxes, though, the rings are “closed” – we see them edge-on. The rings are no more than a few hundred feet thick, so they all but disappear. That makes the planet look much fainter than average. Saturn will reach an equinox in early May, so the rings have basically vanished. They’ll slowly tilt back into view over the coming months, and reach their greatest angle at Saturn’s winter solstice – in 2032. Script by Damond Benningfield

Two bright crescents team up in the early morning the next couple of days: the Moon and the planet Venus – the brilliant “morning star.” They’re quite low as twilight begins to paint the dawn sky. The Moon is an obvious crescent. The Sun illuminates only about one-sixth of the lunar hemisphere that faces our way – the crescent. It’s nighttime across the rest of the lunar disk. It’s not especially dark, though. That’s because that part of the Moon is awash in earthshine – sunlight reflected off of Earth. Earth is much bigger than the Moon, and it’s more reflective. And it’s close to full as seen from the Moon, so the landscape on the nighttime part of the Moon would be much brighter than a moonlit night here on Earth. Venus is a crescent as well. The Sun is lighting almost a quarter of the planet’s Earth-facing hemisphere. But you can’t see Venus’s phase with the eye alone – you need good binoculars or a telescope to see the shape. Venus is fairly close to Earth now, so it’s just about as bright as it ever gets. It appears larger than average, and it’s completely covered by clouds that reflect most of the sunlight that strikes them. Over the next few months, Venus will move farther away from us. But the Sun will light up more of the hemisphere that faces Earth. So Venus will remain a bright presence in the morning sky well into fall. We’ll have more about Venus and the Moon tomorrow. Script by Damond Benningfield

The story of a black hole in Cygnus, the swan, is like the tale of an angler – there’s the star it caught, and the one that got away. V404 Cygni is about 7800 light-years away. It appears fairly close to the star that marks the intersection of the swan’s body and wings, which is high in the sky at dawn. The system was first noticed in 1938, when it flared up – a performance it’s repeated several times. Later, it was discovered that V404 Cygni is a tight binary: a black hole about nine times the mass of the Sun, plus a “normal” star a little less massive than the Sun. The black hole is pulling gas from the companion. The gas forms a disk around the black hole. Every couple of decades, so much gas piles up that it sets off an explosion. That makes the system shine thousands of times brighter. Recently, astronomers found that what looked like a background star probably is bound to the other two. It’s more than 300 billion miles from them. It’s bigger and heavier than the Sun, and is puffing up to become a giant. This third star is about four billion years old – suggesting that the black hole is also that old. The black hole is the corpse of a massive star. Most such stars explode, hurling away any companions. This star must have collapsed completely, without exploding. Since then, it’s consumed at least half of its close companion – but the distant one got away. Script by Damond Benningfield

The most amazing object visible through a small telescope doesn’t look all that remarkable. In fact, it looks like a faint star. Yet that point of light packs the power of 10 trillion Suns – the power of a quasar. 3C 273 is the first quasar ever discovered. When astronomers first saw it, they thought it was just another star. It looks like a star, and its main ingredient is like a star’s as well. But when they measured its distance, they were astonished: 3C 273 was two and a half billion light-years away. That meant it couldn’t be a star at all. Instead, they classified it as a quasi-stellar object – a quasar. Astronomers eventually figured out that it’s powered by a black hole at the heart of a giant galaxy. The black hole is about 900 million times the mass of the Sun. Its enormous gravity pulls in huge amounts of gas and dust, and maybe some stars. That material forms a spinning disk around the black hole. The disk is heated to millions of degrees, so it shines brilliantly – bright enough to see from two and a half billion light-years away. 3C 273 is in Virgo. The constellation’s brightest star, Spica, is low in the southeast at nightfall. The quasar stands high above it, about a third of the way up the sky. Despite its great power, it’s too faint to see with the eye alone. But a telescope reveals this deceptive wonder – a monster masquerading as a star. Script by Damond Benningfield

The mild nights of spring are good times for skywatching. Only one thing is missing: a great meteor shower. The best showers are clustered in fall and winter, with the Perseids of August sometimes joining the list. Although the season doesn’t offer a great shower, a pretty good one should reach its peak tomorrow night: the Lyrids. Under a dark sky, you might see up to a couple of dozen meteors per hour between midnight and dawn. The number of meteors increases closer to dawn, as your part of Earth turns more directly into the meteor stream. Unfortunately, by then the waning Moon will be in the sky, so its light will compete with the fainter meteors. One good thing about meteors, though, is that you don’t have to wait for a shower to see them. A shower occurs when Earth passes through a stream of small bits of dust and rock shed by a comet or asteroid. There are many showers through the year, but only a few are noticeable. But bits of rocky debris are scattered throughout the solar system. So on any dark night, you can see several meteors zipping across the sky. And these “random” meteors can come from any direction and blaze across any part of the sky. So if you have a chance, look for the Lyrid meteor shower in the wee hours of Tuesday morning. If not, then take advantage of just about any clear, dark night to look for meteors flashing across the heavens. Tomorrow: a steady light far across the galaxy. Script by Damond Benningfield

The Sun is four and a half billion years old – a third of the age of the universe. Compared to the stars in globular clusters, though, it’s a youngster. Those stars were born when the universe was young. An example is Messier 3 – a family of about half a million stars. The cluster is about 11.4 billion years old. That means its stars were born just a couple of billion years after the Big Bang. All of the cluster’s remaining original stars are fainter and less massive than the Sun. Anything heavier than the Sun has exhausted its nuclear fuel, leaving only a corpse – a small, dense, faint remnant. And astronomers have seen quite a few of these remnants in M3. But the dead stars are tough to find inside the crowded cluster. Some of the stars of Messier 3 are more massive than the Sun. But they weren’t born that way. Instead, they’ve grown by cannibalizing companion stars. Some of them have pulled gas off the surface of a companion. Others have merged with a companion. Either process adds to a star’s mass. That makes the star brighter and bluer – making it look a lot younger that it really is. This huge cluster of ancient stars is about 34,000 light-years away. It’s in the constellation Canes Venatici, the hunting dogs. M3 isn’t quite bright enough to see with the eye alone, but it’s an easy target for binoculars. It’s well up in the east at nightfall, above the bright star Arcturus. Script by Damond Benningfield

The Lucy spacecraft is headed for the Trojan asteroids – big chunks of rock and metal that share an orbit with Jupiter. But it’s checking out some other sights along the way. This weekend, for example, it’ll pass just a few hundred miles from a body in the asteroid belt, between the orbits of Jupiter and Mars. Lucy is named for the fossilized remains of a human ancestor. The name was selected because the Trojans are fossil remnants of the early solar system. The mission’s current target is 52246 Donaldjohanson – named for the scientist who discovered Lucy half a century ago. The name was chosen after the asteroid was picked as a target for the spacecraft. The asteroid is pretty small – only about two and a half miles in diameter. And Lucy will zip by at 30,000 miles per hour. So it won’t have long to study the target. But its pictures and other observations ought to tell us about the asteroid’s mass, shape, and composition. Donaldjohanson is one of about 2,000 asteroids that are related – they were splintered off a parent body by a big collision. So Lucy’s encounter should tell us not only about Donaldjohanson’s history, but the history of its entire family. This is Lucy’s second encounter with a member of the asteroid belt. After today, the craft isn’t scheduled to check out any other sights along the way. It’ll reach the Trojans in August of 2027. Script by Damond Benningfield

A tight pair of stars got a lot tighter a few years ago. The stars merged, forming a single star. And it’s still settling into its new configuration. V1309 Scorpii produced a brilliant outburst in 2008. At first, it was classified as a classical nova. Such an eruption occurs when a small dead star pulls gas from a close companion. When enough gas piles up, it causes a nuclear explosion. Over the months after V1309 erupted, though, it became clear that something else had happened. The two stars had merged, forming a rare beast called a red nova. The merger produced a brilliant flash, and expelled lots of gas and dust at half a million miles per hour. Continued study showed that the original stars were quite different. One was about half again as massive as the Sun, while the other was just half of the Sun’s mass. Since the outburst, the system has gotten fainter and bluer. That could mean it’s becoming a blue straggler – a star that looks younger and brighter as the result of a merger. Or it could be headed toward a phase known as a planetary nebula – expelling its outer layers, leaving behind only a dead core. Astronomers continue to watch to see what happens. V1309 is in Scorpius, which is low in the southern sky at dawn. Tomorrow, it’s just a tick to the lower left of the Moon. But it’s thousands of light-years away, so it’s too faint to see without a telescope. Script by Damond Benningfield

If you look up the details of W Ursae Majoris, you’ll find that its two stars are about a million miles apart. The way astronomers figure that distance, though, is from the centers of the two stars. When you measure the distance between their surfaces, the stars are a whole lot closer. In fact, they’re touching. That makes them a contact binary – one of thousands discovered so far. Many stars move through the galaxy with one or more companion stars. Their distances from each other vary greatly. Some can be light-years apart. But if they’re born close to one another, they might eventually spiral together. That might be caused by magnetic fields, the exchange of gas between the stars, or some other process. W Ursae Majoris shows how that plays out. One of its stars is a little bigger, heaver, and brighter than the Sun. The other is about half the Sun’s mass. They’re in such close contact that they share their outer layers of gas. That makes them about the same temperature and color. But they’re not the same brightness. As the stars orbit, once every eight hours, they cross in front of one other as seen from Earth. So the system’s brightness varies – the result of sibling stars in a tight embrace. W Ursae Majoris is in the great bear, which includes the Big Dipper. The dipper is high in the sky at nightfall. W Ursae Majoris is well to the upper left of its upside-down bowl, and is visible through binoculars. Script by Damond Benningfield